Effects of canagliflozin on cardiac remodeling and hemodynamic parameters in patients with type 2 diabetes mellitus

Sodium-glucose cotransporter type 2 (SGLT2) inhibitors have demonstrated to reduce cardiovascular risk in patients with type 2 diabetes mellitus (T2DM) in large trials independent of glycemic control. The mechanisms of this cardioprotective property remain uncertain. Evidence suggests positive hemodynamic changes and favorable cardiac remodeling contributing to the clinical outcomes but results were conflicting. We aim to investigate the potential impact on hemodynamic parameters, cardiac structure and functions. This prospective observational study included T2DM patients receiving canagliflozin 100 mg per day in addition to their antidiabetic treatment. We analyzed hemodynamic parameters assessed by echocardiographic measurements and impedance cardiography (ICG) to evaluate systolic and diastolic functions from baseline to 24 weeks after treatment. A total of 47 patients (25 males and 22 females) averaging 64.6 ± 10.9 years had a significant reduction in HbA1c, body weight, and systolic blood pressure. Hematocrit increased significantly, while NT-proBNP remained unchanged. E/e′, left atrium (LA) volume, and LA stiffness were reduced, while left ventricle (LV) global longitudinal strain (GLS) and LA strain rates increased at 24 weeks by conventional and speckle tracking echocardiography. LV mass and ejection fraction showed no differences. ICG suggested significant improvement in hemodynamic parameters with increased stroke volume index and cardiac output index and decreased systemic vascular resistance index at 12 and 24 weeks. Canagliflozin improved hemodynamic parameters and had a favorable impact on LA and LV reverse remodeling. These changes may explain the beneficial effect on cardiovascular outcomes in large clinical trials.


Participants
The target patient population was T2DM patients who had not taken any SGLT2 inhibitor prior to the study.These patients were recruited from outpatients at Hsinchu Mackay Memorial Hospital, Taiwan, and received standard care for T2DM during the study period.Other inclusion criteria were: (1) age ≥ 20 years old, (2) eGFR ≥ 30 mL/ minute/1.73m 2 , and (3) patients taking metformin alone or taking metformin and other antidiabetic drugs.The key exclusion criteria included: (1) patients with type 1 diabetes, (2) pregnant or breastfeeding patients, (3) New York Heart Association (NYHA) Class III and IV, (4) acute or chronic inflammatory disease, (5) patients who are allergic to canagliflozin and its excipients, and (6) severe obesity (BMI ≥ 40 kg/m 2 ).

Echocardiography
Echocardiography was performed by a single trained sonographer blinded to clinical information using a commercially available ultrasound system (GE Vivid 7, GE Medical System, Vingmed, Norway).Standardized echocardiographic measurements were obtained according to the American Society of Echocardiography (ASE) recommendations.Left atrium (LA) and left ventricle (LV) volumes were obtained via the modified biplane Simpson method from the apical two-and four-chamber views.Diastolic function was assessed from early mitral inflow velocity (E), late mitral inflow velocity (A), deceleration time (DT), and tissue Doppler imaging (TDI)-derived mitral annular early diastolic velocity (E′) from LV septal and lateral segments.The mean values of septal and lateral E′ were reported in our tables.
LV and LA strains were assessed by speckle tracking analysis.Baseline 2D images were analyzed offline by manually tracing the endocardial border using proprietary software (version 10.8, EchoPAC, GE Vingmed Ultrasound, Norway).Based on automated speckle-tracking algorithms, LV global longitudinal strain (LV GLS) curves were obtained from the three standard apical views (long-axis, 4-chamber, and 2-chamber).Peak atrial longitudinal strain (PALS) and strain rate (SR) curves (systolic, early, and late diastolic LA strain rate [LA SRs, SRe, and SRa, respectively]) were generated for each atrial segment from apical 2-and 4-chamber views.The

Ethics approval and consent to participate
The study was approved by the Institutional Review Board of MacKay Memorial Hospital (Registration Number: 18MMHIS162e).

Baseline characteristics
From November 2019 to February 2021, 52 T2DM patients were included in the study, and five patients did not complete the study.Three stopped the medication because of adverse drug effects (1 due to dysuria, two due to palpitation), one could not have the examinations due to Covid travel restrictions, and one withdrew consent.Table 1 shows the clinical characteristics of the 47 patients analyzed at baseline.
The mean age of the participants was 64.6 ± 10.9 years.There were 25 (53%) males and 22 (47%) females.The mean body mass index (BMI) and fat content were 28.2 kg/m 2 and 23.3 kg, respectively, indicating that the patients were overweight on average and some had a high body fat percentage.The majority of patients had a history of cardiovascular disease (95.7%), and most were taking antihypertensive medications and statins.The patient's medications, including antihypertensives, diuretics, and antidiabetic agents, remained similar during the study period.
ICG parameters of blood flow and vascular system, including cardiac output, cardiac index, stroke volume, stroke index, and systemic vascular resistance index, showed significant improvement at 12 and 24 weeks after starting canagliflozin.The index of contractility (ICON™) increased significantly, but the other parameters of contractility, including left ventricular ejection time, pre-ejection time, and systolic time ratio, did not change.Unexpectedly, thoracic fluid content (TFC), which reflects the extravascular and intravascular fluid, increased from 24.6 ± 5.3 to 32.7 ± 7.1 k/Ω (p < 0.001).

Discussion
In this prospective study, canagliflozin significantly improved the hemodynamic parameters of blood flow, including stroke volume, stroke index, cardiac output, and cardiac index, as well as systemic vascular resistance by ICG.Furthermore, we observed the beneficial effects of canagliflozin on LV diastolic function and subtle improvement in LA and LV systolic functions evaluated by speckle tracking.The mechanisms underpinning the overwhelming effect of cardiorenal protection by SGLT2 inhibitors are not yet fully understood.It is postulated that SGLT2 inhibitors may augment erythropoiesis and suppress sympathetic hyperactivity [16][17][18] , which are supported by the elevation of hematocrit and reduction of the resting HR and SVRI in this study.Elevated levels of erythropoietin (EPO) increased erythropoiesis and hematocrit and helped reduce the risk of heart failure and ischemic heart disease 19,20 .The reduction of afterload by lowering blood pressure and decreasing vascular resistance likely contributed to the observed overall increase in hemodynamic parameters of blood flow, as well as the improvements in subclinical systolic functions.Studies have demonstrated that SGLT2 inhibitors can directly improver vascular function by inducing vasorelaxation and reducing endothelial cell dysfunction associated with atherogenesis 21,22 ..The decrease in E/e′, indicative of decreased LV filling pressure and diastolic function improvement, is a consistent finding observed in this and other SGLT2 inhibitors' studies [26][27][28] .In the IDDIA trial, E/e′ only decreased significantly during exercise in T2DM patients with dapagliflozin 29 .The other echocardiographic parameters for diastolic function, including LV mass, LA volume, and E/A ratio, are less sensitive.MRI imaging also did not detect an apparent change in the LA or LV geometry 30,31 .Nevertheless, our data from speckle tracking provided additional evidence suggesting beneficial effects on cardiac remodeling and function.LV GLS increased significantly while LVEF did not change, suggesting early and subclinical LV systolic improvement, which was similarly found in other studies 32,33 .The administration of canagliflozin was also associated with significant improvement in LA strain indices and LA stiffness.
To our knowledge, few prior studies reported a comprehensive analysis of LA deformation with the administration of SGLT2 inhibitors.Decreased LA strain and increased LA stiffness have been strongly correlated with atrial fibrillation and adverse clinical outcomes in patients with heart failure with reduced EF (HFrEF) or HFpEF 34,35 .However, our findings contradicted previous studies that found empagliflozin and dapagliflozin had no effect on any hemodynamic parameters evaluated by ICG in T2DM patients at 3 months and 12 weeks, respectively 28,36 .Although all studies enrolled T2DM patients without overt heart failure, there were differences in baseline characteristics.Patients in our study were predominately female, had smaller BMIs, better diabetic control, greater reductions of SBP, and received less diuretic therapy.Additionally, the number of patients enrolled in these studies was limited.
Another possible explanation is that canagliflozin is more selective towards SGLT1 receptors, which are expressed abundantly in the distal proximal tubules of kidneys, the small intestine, and the cardiomyocytes.Suppression of SGLT1 can facilitate glucose uptake, decrease oxidative stress, reduce myocardial fibrosis and ventricular hypertrophy, and improve cardiac function 37,38 .A previous study has shown oxidative stress was strongly associated with impaired myocardial performance and decreased GLS 39 .Dual SGLT1/2 inhibitor, sotagliflozin, has also been shown to reduce the overall risk of cardiovascular death, hospitalization for HF and emergent HF visit 40,41 .Thus, the additional SGLT1 inhibition may potentiate the hemodynamic effect of canagliflozin.
Large clinical trials have recognized the effect of SGLT2 inhibitors in reducing the risk of hospitalization for heart failure, regardless of the presence of diabetes or glycemic control.Furthermore, SGLT2 inhibitors have been found to be effective in non-diabetic patients with HFrEF or HFpEF, who previously had no effective therapy 6,[42][43][44] .Our data suggest that positive cardiac remodeling, improved LV systolic and diastolic functions, and reduced systemic vascular resistance contribute to the broad therapeutic efficacy of SGLT2 inhibitors.Although it is postulated that SGLT2 inhibitors exert a diuretic effect that removes interstitial fluid to reduce the risk of HF, this effect is transient and modest and cannot account for the long-term outcome in clinical trials.In our study cohort, baseline measurements revealed normal level of Nt-proBNP and relatively low TFC.Interestingly, the level of Nt-proBNP did not decrease, and TFC even exhibited an elevation, despite positive hemodynamic changes observed after 6 months of canagliflozin treatment.These findings suggest that other mechanisms may be responsible for the therapeutic effect of SGLT2 inhibitors.The observed increase in TFC may be attributed to the counteracting mechanism of fluid regulation following the inhibition of SGLT2, as evident by the trending elevation in plasma renin activity 45 .
This study has several limitations.Firstly, the non-randomized, uncontrolled design affects the validity of our findings.Secondly, the small sample size and short follow-up duration may limit the generalizability of our results.A large randomized controlled trial is needed to confirm the positive hemodynamic effects of canagliflozin.The small percentage of patients with heart failure also made it difficult to detect the subclinical difference in some endpoints by conventional echocardiography over the 6-month period.Lastly, ICG utilizes the changes in electrical conductivity of the aortic arch blood flow detected by the skin sensors to estimate stroke volume and cardiac output 46 .A recent meta-analysis has indicated limitations in the inability of electrical cardiometry to measure absolute cardiac output values, and it may be applicable as a trend monitor if performed precisely 47 .Factors affecting the tissue and device conductivity, time and postural variability, and different algorithms may influence the calculated values.Nevertheless, our clinical and echocardiographic changes in response to https://doi.org/10.1038/s41598-023-48716-ywww.nature.com/scientificreports/

Table 2 .
Comparison of variables between baseline, 12th and 24th weeks after administration of canagliflozin.Data is mean ± SD for normally distributed data and median and interquartile range for non-normally distributed data.GFR glomerular filtration rate, LDL low density lipoprotein, HDL high density lipoprotein, NT-proBNP N terminal pro B type natriuretic peptide.

Table 3 .
Changes of echocardiographic parameters from baseline to Week 24.EDV end-diastolic volume, ESV end-systolic volume, IVRT isovolumic relaxation time, DT deceleration time, GLS global longitudinal strain, PALS peak atrial longitudinal strain, LA SRs systolic LA strain rate, LA SRe early LA strain rate, LA SRa late LA strain rate.

Table 4 .
Comparison of hemodynamic variables between baseline and 12th and 24th weeks after administration canagliflozin.systolic time ratio = pre-ejection time/left ventricular ejection time.